1 /* (C) 1999-2001 Paul `Rusty' Russell
2  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  */
8 
9 /* Everything about the rules for NAT. */
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11 #include <linux/types.h>
12 #include <linux/ip.h>
13 #include <linux/netfilter.h>
14 #include <linux/netfilter_ipv4.h>
15 #include <linux/module.h>
16 #include <linux/kmod.h>
17 #include <linux/skbuff.h>
18 #include <linux/proc_fs.h>
19 #include <linux/slab.h>
20 #include <net/checksum.h>
21 #include <net/route.h>
22 #include <linux/bitops.h>
23 
24 #include <linux/netfilter_ipv4/ip_tables.h>
25 #include <net/netfilter/nf_nat.h>
26 #include <net/netfilter/nf_nat_core.h>
27 #include <net/netfilter/nf_nat_rule.h>
28 
29 #define NAT_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | \
30 			 (1 << NF_INET_POST_ROUTING) | \
31 			 (1 << NF_INET_LOCAL_OUT) | \
32 			 (1 << NF_INET_LOCAL_IN))
33 
34 static const struct xt_table nat_table = {
35 	.name		= "nat",
36 	.valid_hooks	= NAT_VALID_HOOKS,
37 	.me		= THIS_MODULE,
38 	.af		= NFPROTO_IPV4,
39 };
40 
41 /* Source NAT */
42 static unsigned int
ipt_snat_target(struct sk_buff * skb,const struct xt_action_param * par)43 ipt_snat_target(struct sk_buff *skb, const struct xt_action_param *par)
44 {
45 	struct nf_conn *ct;
46 	enum ip_conntrack_info ctinfo;
47 	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
48 
49 	NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING ||
50 		     par->hooknum == NF_INET_LOCAL_IN);
51 
52 	ct = nf_ct_get(skb, &ctinfo);
53 
54 	/* Connection must be valid and new. */
55 	NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
56 			    ctinfo == IP_CT_RELATED_REPLY));
57 	NF_CT_ASSERT(par->out != NULL);
58 
59 	return nf_nat_setup_info(ct, &mr->range[0], NF_NAT_MANIP_SRC);
60 }
61 
62 static unsigned int
ipt_dnat_target(struct sk_buff * skb,const struct xt_action_param * par)63 ipt_dnat_target(struct sk_buff *skb, const struct xt_action_param *par)
64 {
65 	struct nf_conn *ct;
66 	enum ip_conntrack_info ctinfo;
67 	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
68 
69 	NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
70 		     par->hooknum == NF_INET_LOCAL_OUT);
71 
72 	ct = nf_ct_get(skb, &ctinfo);
73 
74 	/* Connection must be valid and new. */
75 	NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
76 
77 	return nf_nat_setup_info(ct, &mr->range[0], NF_NAT_MANIP_DST);
78 }
79 
ipt_snat_checkentry(const struct xt_tgchk_param * par)80 static int ipt_snat_checkentry(const struct xt_tgchk_param *par)
81 {
82 	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
83 
84 	/* Must be a valid range */
85 	if (mr->rangesize != 1) {
86 		pr_info("SNAT: multiple ranges no longer supported\n");
87 		return -EINVAL;
88 	}
89 	return 0;
90 }
91 
ipt_dnat_checkentry(const struct xt_tgchk_param * par)92 static int ipt_dnat_checkentry(const struct xt_tgchk_param *par)
93 {
94 	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
95 
96 	/* Must be a valid range */
97 	if (mr->rangesize != 1) {
98 		pr_info("DNAT: multiple ranges no longer supported\n");
99 		return -EINVAL;
100 	}
101 	return 0;
102 }
103 
104 static unsigned int
alloc_null_binding(struct nf_conn * ct,unsigned int hooknum)105 alloc_null_binding(struct nf_conn *ct, unsigned int hooknum)
106 {
107 	/* Force range to this IP; let proto decide mapping for
108 	   per-proto parts (hence not NF_NAT_RANGE_PROTO_SPECIFIED).
109 	*/
110 	struct nf_nat_ipv4_range range;
111 
112 	range.flags = 0;
113 	pr_debug("Allocating NULL binding for %p (%pI4)\n", ct,
114 		 HOOK2MANIP(hooknum) == NF_NAT_MANIP_SRC ?
115 		 &ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3.ip :
116 		 &ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3.ip);
117 
118 	return nf_nat_setup_info(ct, &range, HOOK2MANIP(hooknum));
119 }
120 
nf_nat_rule_find(struct sk_buff * skb,unsigned int hooknum,const struct net_device * in,const struct net_device * out,struct nf_conn * ct)121 int nf_nat_rule_find(struct sk_buff *skb,
122 		     unsigned int hooknum,
123 		     const struct net_device *in,
124 		     const struct net_device *out,
125 		     struct nf_conn *ct)
126 {
127 	struct net *net = nf_ct_net(ct);
128 	int ret;
129 
130 	ret = ipt_do_table(skb, hooknum, in, out, net->ipv4.nat_table);
131 
132 	if (ret == NF_ACCEPT) {
133 		if (!nf_nat_initialized(ct, HOOK2MANIP(hooknum)))
134 			/* NUL mapping */
135 			ret = alloc_null_binding(ct, hooknum);
136 	}
137 	return ret;
138 }
139 
140 static struct xt_target ipt_snat_reg __read_mostly = {
141 	.name		= "SNAT",
142 	.target		= ipt_snat_target,
143 	.targetsize	= sizeof(struct nf_nat_ipv4_multi_range_compat),
144 	.table		= "nat",
145 	.hooks		= (1 << NF_INET_POST_ROUTING) | (1 << NF_INET_LOCAL_IN),
146 	.checkentry	= ipt_snat_checkentry,
147 	.family		= AF_INET,
148 };
149 
150 static struct xt_target ipt_dnat_reg __read_mostly = {
151 	.name		= "DNAT",
152 	.target		= ipt_dnat_target,
153 	.targetsize	= sizeof(struct nf_nat_ipv4_multi_range_compat),
154 	.table		= "nat",
155 	.hooks		= (1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT),
156 	.checkentry	= ipt_dnat_checkentry,
157 	.family		= AF_INET,
158 };
159 
nf_nat_rule_net_init(struct net * net)160 static int __net_init nf_nat_rule_net_init(struct net *net)
161 {
162 	struct ipt_replace *repl;
163 
164 	repl = ipt_alloc_initial_table(&nat_table);
165 	if (repl == NULL)
166 		return -ENOMEM;
167 	net->ipv4.nat_table = ipt_register_table(net, &nat_table, repl);
168 	kfree(repl);
169 	if (IS_ERR(net->ipv4.nat_table))
170 		return PTR_ERR(net->ipv4.nat_table);
171 	return 0;
172 }
173 
nf_nat_rule_net_exit(struct net * net)174 static void __net_exit nf_nat_rule_net_exit(struct net *net)
175 {
176 	ipt_unregister_table(net, net->ipv4.nat_table);
177 }
178 
179 static struct pernet_operations nf_nat_rule_net_ops = {
180 	.init = nf_nat_rule_net_init,
181 	.exit = nf_nat_rule_net_exit,
182 };
183 
nf_nat_rule_init(void)184 int __init nf_nat_rule_init(void)
185 {
186 	int ret;
187 
188 	ret = register_pernet_subsys(&nf_nat_rule_net_ops);
189 	if (ret != 0)
190 		goto out;
191 	ret = xt_register_target(&ipt_snat_reg);
192 	if (ret != 0)
193 		goto unregister_table;
194 
195 	ret = xt_register_target(&ipt_dnat_reg);
196 	if (ret != 0)
197 		goto unregister_snat;
198 
199 	return ret;
200 
201  unregister_snat:
202 	xt_unregister_target(&ipt_snat_reg);
203  unregister_table:
204 	unregister_pernet_subsys(&nf_nat_rule_net_ops);
205  out:
206 	return ret;
207 }
208 
nf_nat_rule_cleanup(void)209 void nf_nat_rule_cleanup(void)
210 {
211 	xt_unregister_target(&ipt_dnat_reg);
212 	xt_unregister_target(&ipt_snat_reg);
213 	unregister_pernet_subsys(&nf_nat_rule_net_ops);
214 }
215